There is known a reflective liquid crystal projector using a reflective liquid crystal display panel. The reflective liquid crystal display panel is referred to as LCOS (Liquid Crystal On Silicon). Note that “LCos” is a trademark. The LCOS has a structure in which a liquid crystal is sandwiched between a silicon substrate and a transparent substrate opposed to each other. A liquid crystal driving circuit and pixel electrodes are disposed on the silicon substrate. Light having passed through the transparent substrate and a liquid crystal layer is reflected on the pixel electrodes. In a transmissive liquid crystal device, a pair of transparent substrates is used, and a liquid crystal driving circuit and the like are disposed on one of the transparent substrates, thus causing decrease in aperture ratio. In contrast, in a reflective liquid crystal device, circuits are not disposed on the transparent substrate, thus achieving increase in aperture ratio.
In the reflective liquid crystal projector is used a polarizing beam splitter (PBS) having a function as a polarizer for polarizing illumination light to be incident on a liquid crystal display panel and a function as an analyzer for retrieving image light modulated for each pixel by the liquid crystal display panel. In a common PBS, two right-angle prisms are joined at their diagonal surfaces, and between the joined diagonal surfaces is disposed a polarization separating film. The polarization separating film is a multi-layer film including thin films of high-refractive material and thin films of low-refractive material which are alternately laminated on one another. The polarization separating film separates the illumination light depending on its polarization direction so as to transmit p-polarized light and reflect s-polarized light. Further, there is known a PBS in which a multi-layer reflective polarizing film for use as a polarization separating film is attached to a rigid cover (prism) with use of pressure sensitive adhesives, as disclosed in U.S. Pat. No. 7,234,816 (corresponding to Japanese Patent Translation Publication No. 2007-520756), for example.
An illumination optical system for making illumination light incident on a liquid crystal display panel consists of a light source, a light condensing means, a rod integrator, a relay lens, and the like, for example. An image of an exit end face of the rod integrator is formed on a panel surface of the liquid crystal display panel by the relay lens so as to illuminate an effective reflection region of the panel surface. The illumination range of the illumination optical system to be used depends on a size of the liquid crystal display panel, that is, the effective reflection region.
Recently, in accordance with widespread use of a high definition television, an image to be projected by the reflective liquid crystal projector also has been required to correspond to an aspect ratio of 16:9 as a high definition television size, and the screen size of the panel surface of the liquid crystal display panel comes to have an aspect ratio corresponding to the high definition television size. However, in the case where the illumination range of the illumination light has an approximately circular shape as is conventional, an unnecessary region is applied with the illumination light. For the purpose of eliminating the waste of the illumination light described above, there is proposed a lens for an illumination system including a condenser lens and a cylindrical lens as disclosed in Japanese Patent Laid-Open Publication No. 2009-103807, for example.
However, since the polarizing beam splitter, which consists of two right-angle prisms joined at their diagonal surfaces, and the cylindrical lens as described above are expensive and difficult to miniaturize, they cannot be used in an increasingly-demanded inexpensive portable projector which puts emphasis on downsizing.